Ultrasonics for the Recycling of Lithium Ion Batteries
- Lithium-ion batteries used in electric cars are just now coming to the mass market and with it, recycling capacities must be developed.
- Ultrasonic leaching is an efficient, environmental-friendly technique to recover metals such as Li, Mg, Co, Ni etc. from spent Li-ion batteries.
- Hielscher’s industrial ultrasonic systems for leaching applications are reliable and robust and can be easily integrated into existing recycling plants.
Recycling of Lithium-ion Batteries
Lithium-ion batteries are widely used in electric vehicles (EV), laptops and cell phones. This means that spent lithium-ion batteries are a current challenge regarding waste management and recycling. The batteries are a major cost driver for EVs, and their disposal is expensive, too. Environmental and economical aspects push for a closed recycling loop since the battery waste contains valuable materials and helps to reduce the carbon footprint of manufacturing Lithium-ion batteries.
Recycling of Li-ion batteries is growing to a thriving industry sector in order to ensure the future availability of rare-earth metals and other battery components and to reduce the environmental costs of mining.
Industrial Ultrasonic Leaching
Ultrasonic leaching and metal extraction can be applied to recycling processes of lithium cobalt oxide batteries (e.g. from laptops, smartphones, etc.) as well as of complex lithium-nickel-manganese-cobalt batteries (e.g. from electric vehicles).
High-power ultrasound is well known for its capability to process chemical liquids and slurries in order to improve mass transfer and initiate chemical reactions.
The intense effects of power ultrasonication are based on the phenomenon of acoustic cavitation. By coupling high-power ultrasound into liquids / slurries, the alternating low-pressure and high-pressure waves in liquids generate small vacuum bubbles. The small vacuum voids grow over various low-pressure / high-pressure cycles until the implode violently. The collapsing vacuum bubbles can be considered as microreactors in which temperatures of up to 5000K, pressures of up to 1000atm, and heating and cooling rates above 10-10 occur. Furthermore, strong hydrodynamic shear-forces and liquid jets with up to 280m/s velocity are generated. These extreme conditions of acoustic cavitation create extraordinary physical and chemical conditions in otherwise cold liquids and create a beneficial environment for chemical reactions (sonochemistry).
48kW ultrasonic processor
for demanding applications such as leaching of metals
Ultrasonic leaching of metals from exhausted battery waste.
The great advantage of ultrasonic leaching and metal recovery is the precise control over the process parameters such as amplitude, pressure and temperature. These parameters allow to adjust the reaction conditions exactly to the process medium and the targeted output. Furthermore, ultrasonic leaching removes even the smallest metal particles from the substrate, whilst preserving microstructures. The enhanced metal recovery is due to the ultrasonic creation of highly reactive surfaces, increased reaction rates, and improved mass transport. Sonication processes can be optimized by influencing each parameter and are therefore not only very effective but also highly energy-efficient.
Its exact parameter control and energy efficiency make ultrasonic leaching the favorable and excelling technique – especially when compared to complicated acid leaching and chelation techniques.
Ultrasonic Recovery of LiCoO2 from Spent Lithium-Ion Batteries
Ultrasonication assists the reductive leaching and chemical precipitation, which are are used to recover Li as Li2CO3 and Co as Co(OH)2 from waste lithium-ion batteries.
Zhang et al. (2014) report the successful recovery of LiCoO2 using an ultrasonic reactor. in order to prepare the starting solution of 600mL, they placed 10g of invalid LiCoO2 powder in a beaker and added 2.0mol/L of LiOH solution, which were mixed.
The mixture was poured into the ultrasonic irradiation and the stirring device started, the stirring device was placed in the interior of the reaction container. It was heated to 120◦C, and then the ultrasonic device was set to 800W and the ultrasonic mode of action was set to pulsed duty cycles of 5 sec. ON / 2sec. OFF. The ultrasonic irradiation was applied for 6h, and then the reaction mixture cooled to room temperature. The solid residue was washed several times with deionized water and dried at 80◦C until constant weight. The obtained sample was collected for subsequent testing and battery production. The charge capacity in the first cycle is 134.2mAh/g and the discharge capacity is 133.5mAh/g. The first-time charge and discharge efficiency was 99.5%. After 40 cycles, the discharge capacity is still 132.9mAh/g. (Zhang et al. 2014)
Used LiCoO2 crystals before (a) and after (b) ultrasound treatment at 120◦C for 6h. source: Zhang et al. 2014
Ultrasonic leaching with organic acids such as citric acid is not only effective but also environmentally friendly. Research found that the leaching of Co and Li is more efficient with citric acid than with the inorganic acids H2SO4 and HCl. More than 96% Co and nearly 100% Li were recovered from spent lithium-ion batteries. The fact that organic acids such as citric acid and acetic acid are inexpensive and biodegradable, contributes to further economic and environmental advantages of sonication.
High-Power Industrial Ultrasonics
Hielscher Ultrasonics is your long-experienced supplier for highly efficient and reliable ultrasonic systems, which deliver the required power to leach metals from waste materials. In order to reprocess li-ion batteries by extracting metals such as cobalt, lithium, nickel, and manganese, powerful and robust ultrasonic systems are essential. Hielscher Ultrasonics’ industrial units such as the UIP4000hdT (4kW), UIP10000 (10kW) and UIP16000 (16kW) are the most powerful and robust high-performance ultrasound systems on the market. All our industrial units can be continuously run with very high amplitudes of up to 200µm in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments. Hielscher supplies special sonotrodes and reactors for high temperatures, pressures and corrosive liquids, too. This makes our industrial ultrasonicators most suitable for extractive metallurgy techniques, e.g. hydrometallurgical treatments.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
| Batch Volume | Flow Rate | Recommended Devices |
|---|---|---|
| 0.1 to 20L | 0.2 to 4L/min | UIP2000hdT |
| 10 to 100L | 2 to 10L/min | UIP4000 |
| n.a. | 10 to 100L/min | UIP16000 |
| n.a. | larger | cluster of UIP16000 |
Literature/References
- Golmohammadzadeh R., Rashchi F., Vahidi E. (2017): Recovery of lithium and cobalt from spent lithium-ion batteries using organic acids: Process optimization and kinetic aspects. Waste Management 64, 2017. 244–254.
- Shin S.-M.; Lee D.-W.; Wang J.-P. (2018): Fabrication of Nickel Nanosized Powder from LiNiO2 from Spent Lithium-Ion Battery. Metals 8, 2018.
- Zhang Z., He W., Li G., Xia J., Hu H., Huang J. (2014): Ultrasound-assisted Hydrothermal Renovation of LiCoO2 from the Cathode of Spent Lithium-ion Batteries. Int. J. Electrochem. Sci., 9 (2014). 3691-3700.
- Zhang Z., He W., Li G., Xia J., Hu H., Huang J., Shengbo Z. (2014): Recovery of Lithium Cobalt Oxide Material from the Cathode of Spent Lithium-Ion Batteries. ECS Electrochemistry Letters, 3 (6), 2014. A58-A61.
Facts Worth Knowing
Lithium-Ion Batteries
Lithium-ion batteries (LIB) is the collective terme for (rechargeable) batteries which offer a high energy density and are frequently integrated in consumer electronics such as electronic cars, hybrid cars, laptops, cell phones, iPods, etc.. In comparison to other variants of rechargeable batteries with similar size and capacity, LIBs are significantly lighter.
Unlike the disposable lithium primary battery, a LIB uses intercalated lithium compound instead of metallic lithium as its electrode. The major constituents of an lithium-ion battery are its electrodes – anode and cathode – and the electrolyte.
Most cells share common components in terms of the electrolyte, separator, foils and casing. The major difference between cell technologies is the material utilized as “active materials” such as cathode and anode. Graphite is the most frequently used material as anode, whilst the cathode is made of layered LiMO2 (M = Mn, Co, and Ni), spinel LiMn2O4, or olivine LiFePO4. The electrolyte organic liquid electrolytes (e.g., LiPF6 salt dissolved in a mixture of organic solvents, such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc.) allows for ionic movement.
Depending on the positive (cathode) and negative (anode) electrode materials, the energy density and voltage of LIBs vary respectively.
When used in electric vehicles, often electric-vehicle battery (EVB) or traction battery is used. Such traction batteries are used in forklifts, electric golf carts, floor scrubbers, electric motorcycles, electric cars, trucks, vans, and other electric vehicles.
Metal Recycling from Spent Li-Ion Batteries
In comparison to other types of batteries that often contain lead or cadmium, Li-ion batteries contain less toxic metals and are therefore considered as environmental-friendly. However, the vast amount of spent Li-ion batteries, which will be have to disposed as spent batteries from electric cars, present a waste problem. Therefore, a closed recycling loop of Li-ion batteries is necessary. From an economical point of view, metal elements such as iron, copper, nickel, cobalt, and lithium can be recovered and reused in the production of new batteries. Recycling could prevent a future shortage, too.
Although batteries with higher nickel loadings are coming into the market, it is not possible to produce batteries without cobalt. The higher nickel content comes at a cost: With an increased nickel content, the stability of the battery is decreased and thereby its cycle life and the ability of fast charging are reduced.
Growing demand for Li-ion batteries requests increasing recycling capacities for waste batteries.
Recycling Process
Batteries of electric vehicles such as the Tesla Roadster have an approximate lifetime of 10 years.
The recycling of exhausted Li-ion batteries is a demanding process since high voltage and hazardous chemicals are involved, which comes with the risks of thermal runaway, electrical shock and the emission of hazardous substances.
In order to establish a closed loop recycling, every chemical bond and all elements must be separated into their individual fractions. However, the energy required for such a closed loop recycling are very expensive. The most valuable materials for recovery are metals such as Ni, Co, Cu, Li, etc. since expensive mining and high market prices of metal components make the recycling economically attractive.
The recycling process of Li-ion batteries starts with the dismantling and discharging of the batteries. Before opening the battery, a passivation is required to inactivate the chemicals in the battery. Passivation can be achieved by cryogenic freezing or controlled oxidation. Depending on the battery size, the batteries can be dismantled and disassembled down to the cell. After the dismantling and crushing, the components are isolated by several methods (e.g. screening, sieving, hand picking, magnetic, wet, and ballistic separation) in order to remove cell casings, aluminium, copper and plastics from the electrode powder. The separation of the electrode materials is necessary for the downstream processes, e.g. hydrometallurgical treatment.
Pyrolysis
For pyrolytic processing, shredded batteries are smelted in a furnace where limestone is added as a slag-forming agent.
Hydrothermal Processes
Hydrometallurgical processing is based on acid reactions in order to precipitate the salts as metals. Typical hydrometallurgical processes include leaching, precipitation, ion exchange, solvent extraction and electrolysis of aqueous solutions.
The advantage of hydrothermal processing is the high recovery yield of +95% of Ni and Co as salts, +90% of Li can be precipitated, and the rest can be recovered up to +80%.
Especially cobalt is a critical component in lithium-ion battery cathodes for high energy and power applications.
Current hybrid cars such as the Toyota Prius, use nickel metal hydride batteries, which are dismantled, discharged and recycled in similar way as Li-ion batteries.
Powerful sonication from lab and bench-top to industrial production.